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Climate Change Could Alter Face of Forests: Johnstone

Above is a media file of the interview Johnstone did with CBC Radio's Quirks and Quarks.

By Kirk Sibbald

A University of Saskatchewan researcher says climate warming could soon change the face of Canadian forests.

Jill Johnstone, associate professor of biology in the College of Arts & Science, is co-author of a recently released paper that argues a predicted increase in forest fires could reduce the ability of conifers—such as black spruce and jack pine, to regenerate.

The boreal forests in Canada, including those in Saskatchewan, are dominated by serotinous conifers, which produce cones that stay sealed and closed on the top of tree canopies. However, once triggered by the heat of a forest fire, triggers cones to open and release seed onto the post-fire forest floor, ensuring the forest’s regeneration. Similar adaptations have been found in fire-prone regions of Western Australia and the United States.

With many climate models predicting an increase in fire activity due to climate warming, the paper’s authors argue this may disrupt such processes.

Work conducted by Johnstone and former U of S PhD student Carissa Brown demonstrated fires recurring in the same place after a short period (about 30 years) can severely disrupt the ability of serotinous pine and spruce to regenerate following fires. This is because the cones on young trees are too sparse and close to the ground to survive the second fire.

In such situations, the forest will often evolve and become dominated by new types of vegetation, like aspens or open shrubs.

“The important contribution of this paper is that we have presented a model that allows us to anticipate what parts of the boreal forest are likely to be particularly sensitive to an increase in fire frequency, said Johnstone. “The forests of northern Saskatchewan are certainly in one potential hot-spot of change, and we should anticipate the potential for large changes in types of forest cover in the more fire-prone regions of our province.”

The research paper, The Impacts of Changing Disturbance Regimes on Serotinous Plant Populations and Communities, appeared in the Oct. 11 issue of Bioscience. Johnstone and Brown co-authored the paper alongside Brian Burma (University of Alaska Southeast), Dan Donato (Washington State Department of Natural Resources) and Joseph Fontaine (Murdoch University, Australia).